1. Field of the Invention
The present invention relates to electric generators for bicycles and, more particularly, to an electric generator assembly detachably securable to a bicycle wheel.
2. Description of the Related Art
Electric generators or dynamos such as, for example, hub dynamos and tire dynamos have been developed to supply electrical power to lighting devices installed on bicycles. Hub dynamos, as the name implies, are disposed within the hubs of bicycle wheels, typically the front wheels, and are typically installed during manufacturing of new bicycles. Because a hub dynamo forms an integral part of a wheel hub, an already assembled bicycle cannot be easily retrofitted with a hub dynamo without major modifications. Retrofitting is difficult for the additional reason that the hub dynamos must first be spoked into the wheels. Thus, in addition to the high manufacturing costs of hub dynamos, there are also high assembly costs for mounting them on the wheels.
Tire dynamos, on the other hand, are inexpensive and can be easily installed on already assembled bicycles; however, since these devices are frictionally driven by bicycle tires, they tend to increase tire wear and are relatively inefficient. Furthermore, the ability of the tire dynamos to generate electricity decreases when the tire becomes wet due to adverse weather conditions.
DE 90 02 898 U1 discloses a hub dynamo with a stator and an armature as its main components. The stator and armature rotate relative to each other in a hub which rotates about a stationary axis. A planetary gear system is arranged between the armature and the stator so that the armature rotates at a speed higher than that of the stator and in a direction opposite to that of the stator. The planetary gear system is selectively disengageable by a bicyclist,
Similarly, DE 93 00 311 U1 discloses a hub dynamo which forms an integral portion of a hub and is driven by a multiple planetary gear system. The planetary gear system can be engaged or disengaged through an inner coupling which is actuatable from outside the hub.
Accordingly, there is a need for a low-cost energy-efficient dynamo that can be easily installed on an already assembled bicycle.